In the field of magnetic heads to be mounted on a magnetic recording apparatus such as a hard disk drive (HDD), recently, the recording method is being shifted from longitudinal recording to perpendicular recording in order to improve the recording density with respect to a magnetic recording medium such as a hard disk. The perpendicular recording method provides not only a high linear recording density but also an advantage that the recording medium after recording is less influenced by thermal fluctuation.
In the magnetic head according to the perpendicular recording method, when the drive system is a rotary actuator, generally, a recording medium facing surface of a main magnetic pole has an inverted trapezoidal shape whose longer and shorter sides are located on trailing and leading sides, respectively, or an inverted triangular shape whose base is located on a trailing side for avoiding the problem of side erase, wherein the longer side or the base is defined as a track width of the main magnetic pole. It should be noted that the “side erase” refers to a problem that a skew angle between a central axis of the magnetic head and a line tangent to a track of a magnetic disk being the recording medium increases at radially inner and outer sides of the magnetic disk, and as a result, the leading side of the main magnetic pole partially protrudes into an adjacent track, thereby erasing information recorded on the track.
For formation of the main magnetic pole, generally, there has been employed a manufacturing method using dry etching by ion milling. In the ion milling, the main magnetic pole film may be shaped into a given shape by changing an irradiation angle of an ion beam on demand, but in this case, since a small-width portion whose section has the inverted trapezoidal or triangular shape is disposed in side-by-side relationship with a non-magnetic film such as of alumina and the main magnetic pole film has a higher etching rate, the main magnetic pole film is etched more at a central area which is less protected by the non-magnetic film, causing a problem that the inverted trapezoidal or triangular shape is recessed at the trailing side (i.e., at the longer side or the base) into an arc shape.
Contrarily, for example, US Unexamined Patent Application Publication No. 2006/0098339 (Japanese Unexamined Patent Application Publication No. 2006-134507) discloses a technology of purposefully forming an arcuate recess at the trailing side of the inverted trapezoidal shape. This technology can control the radius of curvature of the recess with a high accuracy and thus will never cause a problem, but in the case where the above technology cannot be employed on account of the manufacturing process of the magnetic head and the recess is formed without any purpose as described above, the recess becomes inaccurate, which is totally undesirable because it leads to unevenness in the inverted trapezoidal or triangular shape.
Since the above problem occurs when forming a thin film layer including a plurality of thin films having different etching rates, it is not typical of the manufacturing process of the magnetic head but also unavoidable in the manufacturing process of other electronic component elements such as an integrated circuit as long as having such a thin film layer structure.